| At this moment,it is difficult to realize the central heating system in rural areas because of the scattered courtyards,long transmission distance from towns and the difficulties to install the heating pipelines.According to the investigation,the decentralized heating equipment(such as the small furnaces)with low efficiency is still the main heating system in rural area and has resulted in serious environmental pollution and a decline in the living quality for the residents.In order to alleviate the environmental pollution caused in rural areas,the feasibility of solar-air source heat pump hybrid system for heating and hot water supplying in residential buildings in Shandong area is analyzed in this paper.Three different forms of the hybrid heating systems have been put forward.The simulation model for each form of the system has been developed respectively and the energy consumption of each model has been compared and analyzed based on the stimulation results.And finally the best system form among these three systems has been confirmed and its optimal operation control strategy has been obtained in this paper.The heating status in different rural areas of Shandong Province were investigated,focused on the rural areas in Yantai City,Jinan City and Heze City respectively representing the eastern,central and western regions of Shandong Province.It is found the heated kang is treated as the main heat source for heating in rural areas of Yantai City;and small heating furnaces become local residents'main heating methods in the rural areas in Jinan and Heze.Based on the investigation results and the local renewable energy distribution,three kinds of heating systems:air-source heat pump system,solar-air source heat pump hybrid systems in serial connection and the hybrid system in parallel have been proposed.In this paper,a typical residential building was taken as an case study.The hourly heating load of a residential building under different heating supply modes have been calculated by the software(DeST),and the simulation models have been established under the TRNSYS platform.The system performance and the energy consumption have been investigated.The results indicate that the hybrid system in parallel connection mode has the highest values of the system COP,the solar collection efficiency and solar heating guarantee rate under the nine working conditions proposed in this paper.The annual operation cost of the single air source heat pump system,the solar-air source heat pump hybrid system in parallel and the small coal-fired furnace has been calculated and compared.The results show that the annual cost of the hybrid system in parallel connection is the lowest,which is 5193 yuan per year,and the annual cost of coal-fired heating furnace reaches the highest value,8244 yuan per year.Thirdly,the design of the hybrid system in parallel connection has been optimized by means of the software(TRNOPT)taking the overall cost as the optimal control goal.For the case study of the typical residential building with an area of 220m,the optimized solar collector area is 32m~2 and the thermal storage temperatures(?T1 and?T2)on the collector side are 9?and2.5?respectively.In this case,the comprehensive cost reaches the lowest point,which is55113 yuan for the whole operation of 15 years.Finally,the energy benefit and environmental benefit of the single air source heat pump system,pre-optimized parallel hybrid system,optimized hybrid system and the small coal-fired heating system have been analyzed and compared.The results show the annual cost of the optimized parallel hybrid system(4975 yuan a year)is the lowest,and has good environmental benefits.The solar-air hybrid heating system proposed in this paper has advantages of good economic and environmental benefits,stable operation,easy installation and operation.The optimization results can provide a good guideline for the application of the solar-air source heat pump system in Shandong rural region. |
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